The success of agriculture is affected by a number of different factors. Cultivated plants are often prone to attack by pests, viruses, bacteria and fungal diseases. In the search for a way of fighting such attacks over the last century, preparations containing synthetic chemical compounds have been developed. Such chemical compounds include chlorinated hydrocarbons (DDT, HCH), organic phosphoric-acid esters, compounds containing sulphur and phosphorus, and even toxic heavy metals (Bi, Hg, Tl), which were proven to be effective plant protection chemicals. This led to an increased use of chemical compounds in order to increase yield and at the beginning dramatic increases in yields were indeed observed.
This success led to a separate industrial branch to be formed dedicated to the discovery, development and preparation of more effective plant protection agents and preparations. Over the years, particularly in recent times, it has become increasingly evident that the agent residues and decomposition products found in the crops intended for feeding or for human consumption may have serious health consequences. This has led to an increased awareness and a need to control the use of plant protection agents.
The situation has been worsened by the resistance of the pests to plant protection agents, which has resulted in increased doses being required. There has been a need to provide new and more effective chemical compounds to overcome the developing problems. However, it has been recognized that part of the chemical plant protection agents accumulate in the plants, which are passed on when consumed by animals or humans, having potentially serious health damaging risks. As a consequence of the effects mentioned above, increasing regulations have been imposed and in some cases effective chemical plant protection agents were even banned in many countries. The search for alternative compositions for plant protection, which work within the new stringent regulations of recent years continues. There have been attempts to implement biotechnological methods to combat the problem, such as for the induction of viral resistance (see, e.g., HU 223 266), the use of a new strain of Pseudomonas chlororaphis bacterium as an active ingredient in the protection against plant diseases (see HU 220 582) and plant conditioning compositions of purely natural origin comprising extracts (WO 2010/150034). WO 2010/150034 found that effective plant protection preparations could only be produced by combining the extracts from no less than four different sorts of plants; i.e., willow, poplar, nut and nettle extract. All extracts from the four different plants were extracted in water. Such preparations suffer the drawbacks that they rely on extracts from many different natural sources, which can be very expensive, complicated to produce and less reliable due to the many processes required to obtain the end product.
It is known that some plant species can produce natural substances that provide protection against different pests. One known plant of this type is the white willow (Salix alba) belonging to the willows (Salicaceae). It was observed even by the American settlers dealing with basketry, that the steeping liquor enhancing the flexibility of the wicker was effective against some plant pests (see wintergreen oil, betula oil). Salicylic acid methyl ester could be identified as main active ingredient (see: [1] Organic Molecules in Action, Goodman, Morehouse, Gordon and Breach, 1973; [2] British Pharmaceutical Codex 1911: METHYLIS SALICYLAS; [3] FAO Nutrition Meetings Report Series No. 44A WHO/Food Add./68.33, Toxicological Evaluation of Same Flavouring Substances and Non-Nutritive Sweetening Agents). This has led to derivatives of salicylic acid being developed for use as plant protection agents, as can be seen in the patent applications HU 214 217 and HU 207 855.
Furthermore, it is also known that the concoction of the leaves of some nettles (Urticaceae) can be used for spraying horticultural plants. The main active ingredients of the concoction are: formic acid, tan substances, resins, nettle toxin, etc. For example patent applications HU 226 041 and HU 225 901 relate to the preparations containing among others nettle and these preparations are recommended for limited applications in fields, such as the cultivation of some plants and for the preparation of the soil.
The goal of this invention is to provide plant protection preparations that increase the resistance of a plant to diseases. It is a further goal to provide plant protection preparations that are practical and economical to produce and environmentally compatible.